How do I retain the outer XML of sub-elements?

I have an XML file that contains a list of individual <order/> elements. I would like to split this single XML file up into multiple files, each of which contain a single order.

Example input file:

<!-- language: lang-xml -->

<orders>
  <order order-id="123">
    <line-item product-id="ABC">ABC</line-item>
  </order>
  <order order-id="456">
    <line-item product-id="DEF">DEF</line-item>
  </order>
</orders>

Desired outputs:

> Order-123.xml:
>
> <order order-id="123">
> <line-item product-id="ABC">ABC</line-item>
> </order>
>
> Order-456.xml:
>
> <order order-id="456">
> <line-item product-id="DEF">DEF</line-item>
> </order>

At this stage, I am not concerned with unmarshalling each of the order details into a struct; I merely want an exact copy of each <order/> node in its own file.

I have tried a few variations of this using xml:",innerxml", like this:

<!-- language: lang-golang -->

type OrdersRaw struct {
  Orders []OrderRaw `xml:"order"`
}
type OrderRaw struct {
  Order string `xml:",innerxml"`
}

The problem in the above code is that each Order value contains the inner XML (starting with <line-item/>) but does not contain the wrapping <order/> tag.

Ideally, if there were an xml:",outerxml" tag, it would serve my purpose.

I am trying to avoid doing hacky things like manually concatenating the inner XML with handwritten XML (e.g. <order order-id="123">).

Use XMLName on your OrderRaw:

type OrderRaw struct {
	XMLName xml.Name `xml:"order"`
	Order   string   `xml:",innerxml"`
	OrderID string   `xml:"order-id,attr"`
}

Playground: https://play.golang.org/p/onK5FExqzD.

EDIT: If you want to save all attributes, you'll have to use MarshalerXML and UnmarshalerXML interfaces:

func (o *OrderRaw) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	o.attrs = map[xml.Name]string{}
	for _, a := range start.Attr {
		o.attrs[a.Name] = a.Value
	}
	type order OrderRaw
	return d.DecodeElement((*order)(o), &start)
}
func (o OrderRaw) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	for name, attr := range o.attrs {
		start.Attr = append(start.Attr, xml.Attr{Name: name, Value: attr})
	}
	start.Name = xml.Name{Local: "order"}
	type order OrderRaw
	return e.EncodeElement(order(o), start)
}

Playground: https://play.golang.org/p/XhkwqJFyMd.